1. Field of the Invention
The present invention relates generally to a laser diode having a double heterostructure in a strip-shaped ridge.
2. Description of the Related Art
In U.S. Pat. No. 4,352,187 and in the publication "Frequenz . . . ", vol. 34 (1980), pages 343 through 346, is disclosed a metal clad ridge waveguide (MCRW) laser diode having a semiconductor layer double hetero-layer structure and a strip-shaped ridge with a contact coating. For improved waveguide performance, the laser diode is provided with a third layer of the double hetero-layer structure which has reduced thickness laterally of the ridge, the strip-shaped web having a width of between 2 to 10 .mu.m.
The contact coating of the laser diode extends from the upper side of the ridge down over the sidewalls of the ridge to the surface of the reduced thickness third layer of the double heter-layer structure. To obtain an optimum waveguide performance for the laser emission which is generated in the laser-active second layer of the hetero-layer structure, it is necessary to provide a residual thickness of the third layer of the double hetero-layer structure.
In FIG. 1 of the publication "Frequenz . . . ", a mesa format is identified having a layer structure with a width of 150 .mu.m. Such layer structure format is not to be confused with a ridge in the sense of a metal clad ridge waveguide laser diode. No wave guidance based on the principle of MCRW laser diodes whatsoever comes into consideration given such a width of the disclosed format.